Combinatorial Treatment Strategy of 177Lu-PSMA-617 and Docetaxel Chemotherapy in Highly PSMA- and FDG-Avid (Pro-PET Score 3) Metastatic Castration-Resistant Prostate Cancer While Considering Pre-taxane PRLT

Abstract 177Lu-PSMA-617 targeted radioligand therapy (RLT) received U.S. Food and Drug Administration approval in 2022 for metastatic castration-resistant prostate cancer (mCRPC) patients progressing after androgen receptor pathway inhibitors and taxane chemotherapy. Despite its efficacy, response rates vary, prompting investigation into combination approaches with other chemotherapy agents to improve outcomes. Few trials and case studies have explored the option of combining radionuclide therapy with taxane-based chemotherapy and have shown favorable outcomes. Herein, we report a case of a 71-year-old man diagnosed with mCRPC referred for prostate-specific membrane antigen (PSMA) RLT after progression on hormonal therapy and radiotherapy. Baseline dual-tracer positron emission tomography (PET) (68Ga-PSMA-11 and 18F-fluorodeoxyglucose [FDG]) scans showed intense PSMA expressing and FDG concentrating matched extensive skeletal metastatic lesions (Pro-PET score 3) and therefore was planned for PSMA RLT in combination with docetaxel therapy. An excellent clinical and favorable biochemical and scan response was observed after first cycle of PSMA RLT and three cycles of docetaxel therapy with no toxicity. The patient underwent further second cycle of PSMA RLT and two more cycles of docetaxel in view of favorable response to the previous cycle. Response evaluation with dual-tracer PET scans showed progressive skeletal lesions but with continued excellent symptomatic benefit and fall in serum prostate-specific antigen levels. The present case report highlights the importance of dual-tracer PET scans and Pro-PET scoring in deciding the further course of management in cases with progressive mCRPC cases.